User`s manual

53
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER with CLOSED CAPTION DECODER
and ON-SCREEN DISPLAY CONTROLLER
MITSUBISHI MICROCOMPUTERS
Rev. 1.0
M37281MAH–XXXSP,M37281MFH–XXXSP
M37281MKH–XXXSP,M37281EKSP
8.8.8 Definition of A-D Conversion Accuracy
The definition of A-D conversion accuracy is described below (refer
to Figure 8.8.4).
Accuracy is shown the difference between measurement result out-
put code and output code which is expected for A-D conversion whose
specification is ideal by using LSB.
The analog input voltage in accuracy measurement is made to be a
middle point of input voltage width (=1 LSB) which outputs the code
in which the A-D converter with the ideal characteristics is identical.
For example, 1 LSB’s width is 20 mV at VREF = 5.12V.
0 mV, 20 mV, 40 mV and 60 mV are selected for analog input voltage.
A-D conversion accuracy is shown in Fig 8.8.4.
That the output code expected in the ideal A-D converter is “0516”
shows that there is actual A-D conversion result with in “0316” to “0716”
on the = ±2LSB absolute accuracy, when the analog input voltage is
100 mV.
And, zero error and scale error are contained for the absolute accu-
racy, and the quantization error is not contained.
Fig. 8.8.4 Definition of A-D Conversion Accuracy
Output code
0
Analog input voltage (mV)
20 40 80 100 120 140 160 180 200 220
0016
0116
0216
0316
0416
0516
0616
0716
0816
0916
+ 2LSB
– 2LSB
60
Absolute accuracy
Limitless resolution A-D
conversion characteristics
Ideal A-D conversion
characteristics